1. Technical Field
The present invention relates to a piezoelectric device, a piezoelectric module, and an electronic apparatus.
2. Related Art
In the related art, an ultrasonic sensor including a plurality of ultrasonic transducers mounted on a sensor substrate has been known (for example, JP-A-2012-152319).
The ultrasonic sensor disclosed in JP-A-2012-152319 mentioned above includes, for example, a matrix-like two-dimensional array structure in which four ultrasonic transducers are disposed on the sensor substrate at equal intervals along an X-axis and a Y-axis. However, such a two-dimensional array structure has a problem that wirings connected to the ultrasonic transducers become complicated.
In order to solve the above-described problem, an ultrasonic probe using a through electrode has been known (for example, Pamphlet of International Publication WO 2009/139400).
The ultrasonic probe disclosed in Pamphlet of International Publication WO 2009/139400 mentioned above includes a plurality of vibration elements each of which an electromechanical coupling coefficient or sensitivity changes depending on a bias voltage. Each of the vibration elements includes a substrate, a first film provided on the substrate, a lower electrode provided within the first film, a frame provided on the first film, a second film provided on the frame, and an upper electrode provided within the second film. In addition, the frame is provided with an opening, and an internal space (vacuum) is formed between the first film and the second film by the opening. This cMUT chip applies a pulse voltage between the lower electrode and the upper electrode to thereby vibrate the second film facing the internal space and transmit ultrasonic waves to a side opposite to the substrate.
Through holes passing through the substrate, that is, through electrodes are provided corresponding to the upper electrode and the lower electrode of the cMUT chip, and the through electrodes are connected to a signal pattern provided on a flexible substrate through the substrate. With such a configuration, the simplification of wirings is achieved.
Incidentally, in the ultrasonic probe disclosed in Pamphlet of International Publication WO 2009/139400 mentioned above, the simplification of wirings is achieved by the through electrodes, and the through electrodes are provided in the substrate. Accordingly, the strength of the element substrate is reduced, which leads to a tendency for the element substrate to be damaged. On the other hand, a configuration in which the element substrate is strengthened by providing a reinforcement plate (sealing plate) is also considered. However, the above-mentioned cMUT chip is configured such that ultrasonic waves are output by vibrating the second film side, and thus a reinforcement plate cannot be provided on the second film side. Accordingly, in a case where a reinforcement plate is provided, it is necessary to provide the reinforcement plate on a side opposite to the first and second films of the substrate. In this case, finally, through electrodes are provided in both the reinforcement plate and the substrate, which results in a problem of the insufficiency of strength.